WordPress at a glance
function is not described

wp_imagecreatetruecolor() WP 2.9.0

Create new GD image resource with transparency support

No Hooks.

Return

resource. The GD image resource.

Usage

wp_imagecreatetruecolor( $width, $height );
$width(int) (required)
Image width in pixels.
$height(int) (required)
Image height in pixels..

Code of wp imagecreatetruecolor: wp-includes/media.php WP 5.2.2

<?php
function wp_imagecreatetruecolor( $width, $height ) {
	$img = imagecreatetruecolor( $width, $height );
	if ( is_resource( $img ) && function_exists( 'imagealphablending' ) && function_exists( 'imagesavealpha' ) ) {
		imagealphablending( $img, false );
		imagesavealpha( $img, true );
	}
	return $img;
}